RESUMO
T cell production of IFN-gamma contributes to host defense against infection by intracellular pathogens, including mycobacteria. Lepromatous leprosy, the disseminated form of infection caused by Mycobacterium leprae, is characterized by loss of cellular response against the pathogen and diminished Th1 cytokine production. Relieving bacterial burden in Ag-unresponsive patients might be achieved through alternative receptors that stimulate IFN-gamma production. We have previously shown that ligation of signaling lymphocytic activation molecule (SLAM) enhances IFN-gamma in mycobacterial infection; therefore, we investigated molecular pathways leading from SLAM activation to IFN-gamma production in human leprosy. The expression of the SLAM-associated protein (an inhibitory factor for IFN-gamma induction) on M. leprae-stimulated cells from leprosy patients was inversely correlated to IFN-gamma production. However, SLAM ligation or exposure of cells from lepromatous patients to a proinflammatory microenvironment down-regulated SLAM-associated protein expression. Moreover, SLAM activation induced a sequence of signaling proteins, including activation of the NF-kappaB complex, phosphorylation of Stat1, and induction of T-bet expression, resulting in the promotion of IFN-gamma production, a pathway that remains quiescent in response to Ag in lepromatous patients. Therefore, our findings reveal a cascade of molecular events during signaling through SLAM in leprosy that cooperate to induce IFN-gamma production and strongly suggest that SLAM might be a focal point for therapeutic modulation of T cell cytokine responses in diseases characterized by dysfunctional Th2 responses.
Assuntos
Adjuvantes Imunológicos/fisiologia , Glicoproteínas/fisiologia , Imunoglobulinas/fisiologia , Líquido Intracelular/imunologia , Líquido Intracelular/microbiologia , Peptídeos e Proteínas de Sinalização Intracelular , Mycobacterium leprae/imunologia , Transdução de Sinais/imunologia , Células Th1/imunologia , Células Th1/metabolismo , Adjuvantes Imunológicos/metabolismo , Antígenos CD , Proteínas de Transporte/antagonistas & inibidores , Proteínas de Transporte/biossíntese , Células Cultivadas , Citocinas/fisiologia , Proteínas de Ligação a DNA/metabolismo , Regulação para Baixo/imunologia , Glicoproteínas/imunologia , Glicoproteínas/metabolismo , Humanos , Imunoglobulinas/imunologia , Imunoglobulinas/metabolismo , Líquido Intracelular/enzimologia , Líquido Intracelular/metabolismo , Hanseníase/enzimologia , Hanseníase/imunologia , Hanseníase/metabolismo , Ligantes , Ativação Linfocitária/imunologia , NF-kappa B/metabolismo , Transporte Proteico/imunologia , Proteínas Tirosina Quinases/metabolismo , Proteínas Proto-Oncogênicas/biossíntese , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-fyn , Receptores de Superfície Celular , Fator de Transcrição STAT1 , Índice de Gravidade de Doença , Proteína Associada à Molécula de Sinalização da Ativação Linfocitária , Membro 1 da Família de Moléculas de Sinalização da Ativação Linfocitária , Proteínas com Domínio T , Células Th1/enzimologia , Células Th1/microbiologia , Transativadores/metabolismo , Fatores de Transcrição/biossínteseRESUMO
We have previously identified that Leishmania mexicana cysteine proteases (CPs) are virulence factors. We have now produced a recombinant L. mexicana CP, CPB2.8, which has similar enzymatic activity to native enzyme. Inoculation of CPB2.8 (< or =5 microg) into the footpads of BALB/c mice not only up-regulated mRNA transcripts for IL-4 and IL-4 production in the draining popliteal lymph nodes, but also polarized splenocyte anti-CD3 stimulated responses toward a Th2 bias as measured by increased IL-5 production compared with controls. In agreement with promoting a Th2 response, CPB2.8 also induced strong specific IgE responses in treated mice as well as increasing whole IgE levels. Inhibition of the enzyme activity of CPB2.8 by treatment with E-64 ablated the enzyme's ability to induce IgE. Significantly, infection of mice with CPB-deficient parasites failed to stimulate production of IgE, unlike infection with wild-type parasites. Furthermore, enzymatically active (<0.1 U/ml) but not E-64-inactivated CPB2.8 was able to proteolytically cleave CD23 and CD25, although not B220 or CD4 from murine lymphocytes. These properties are similar to those demonstrated by the house dust mite allergen Der p I and provide an explanation for the immunomodulatory activity of the CPB2.8 virulence factor. Vaccination with CPB2.8 enhanced L. mexicana lesion growth compared with control animals. Nevertheless, vaccination with IL-12 and CPB2.8 resulted in a degree of protection associated with inhibition of lesion growth and a Th1 response. Thus, CPB2.8 is a potent Th2-inducing molecule capable of significant vaccine potential if administered with a suitable adjuvant.